This invention relates to shingling and stacking of conveyed sheet material, such as corrugated paperboard and the like.
In the manufacture of paperboard products such as boxes, the paperboard is often played out from a source such as a large roll, cut into separate sheets, stacked and then suitably further processed into the desired product. The entire operation is necessarily accomplished at high speed because of the large volume of products to be made. The conveying devices between the different stations must operate swiftly and accurately.
It has been previously been suggested, as in the above-identified U.S. Pat. No. 3,565,423, to utilize a shingling device upstream of a sheet stacker to shorten the length of the total conveyor needed.
It is an aim of the present invention to provide an improved concept for conveying, shingling and stacking sheet material wherein a pre-determined number of sheets are to be stacked at a time and then discharged before the next stack forming is commenced. It is a further aim of the invention to speed up the transfer of the shingled sheets to the stacker and to start the stacker discharge cycle once the total number of conveyed sheets to be stacked in a single stack have passed a selected point on the line. It is also an aim of the present invention to hold back the upstream sheets on and downstream of the shingling conveyor, without stopping their movement, while the stacker is discharging. In addition, it is an aim of the invention to accomplish the above-mentioned aims automatically.
The invention contemplates utilization of a conveyor system wherein sheets are conveyed from a cutter or the like at a given speed, are increased in speed before passing through a diverter, are slowed down after passing through a shingling nip to thereby overlap them, and then normally proceed at the latter speed to a stacker which is adapted to stack a fixed number of sheets before discharging the stack.
In accordance with one aspect of the invention, a sheet sensor is disposed upstream of the diverter to count the number of sheets and, when the requisite number of sheets have passed, triggers the cycle for ultimate discharge of all downstream sheets in a single stack.
In accordance with another aspect of the invention, the first phase of the discharge cycle includes speeding up of the conveyor line downstream of the shingling nip to move the downstream sheets away from those upstream which will be disposed in the next succeeding stack.
In accordance with a further aspect of the invention, a sheet position sensing means is utilized, and as the trailing end of the group of fast-moving downstream sheets passes selected points, the shingle conveyor sections upstream thereof are slowed to partially delay the sheets which will form the next stack in their movement down the conveyor. When all of the sheets destined for the stack are in the stacker, the stacker is actuated to discharge the stack and thereupon the conveyors downstream of the shingling nip are slowly returned to their original normal speed for conveying the sheets which will form the next succeeding stack. All of this is accomplished automatically.